1. Field of the Invention
The present invention relates to a straddle-type vehicle provided with a belt type continuously variable transmission (CVT) having a resin-block-type belt.
2. Description of Related Art
Straddle-type vehicles, such as a motorcycle, provided with a belt type CVT are known (see JP-A-2002-147582, for example).
A belt type CVT includes a V-belt wound around a primary sheave and a secondary sheave. Driving force of an engine is transmitted via a crankshaft to the primary sheave, the V-belt, and the secondary sheave in this order to change a speed ratio, and is thereafter transmitted to drive wheels. The primary sheave, the V-belt, and the secondary sheave are housed in a belt chamber defined in a transmission casing.
In the motorcycle of JP-A-2002-147582, a resin-block-type belt is employed as a V-belt to improve durability of the V-belt and to prevent heat liberation due to deformation of the V-belt. The resin-block-type belt includes a number of resin blocks and a coupling member for coupling the resin blocks. However, being independent of each other, the resin blocks are likely to collide with each other as the belt runs. Accordingly, the resin-block-type belt is prone to make more noise relative to a rubber belt.
To this end, in order to suppress noise, JP-A-2002-147582 proposes providing a sound absorber on an inner surface of a transmission casing that accommodates the resin-block-type belt.
The V-belt, and the primary and secondary sheaves wound by the V-belt rotate at a high speed. This necessitates locating the sound absorber so as not to come into contact with the V-belt or sheaves. In other words, the sound absorber must be positioned away from the V-belt and sheaves by a certain distance. Accordingly, when the sound absorber is provided on an inner surface of a transmission casing, as in JP-A-2002-147582, space in the transmission casing for the sound absorber must be secured in advance. However, securing additional space for the sound absorber increases the volume of the belt chamber. Thus, the motorcycle of JP-A-2002-147582 has a disadvantage in increased size of the continuously variable transmission.
In addition, sound absorbers generally have heat-retaining properties. Accordingly, the temperature inside the belt chamber in which a sound absorber is provided on the inner surface of the transmission casing easily rises. This leads to another problem in that, as the temperature of the belt chamber rises, the durability of the resin-block-type belt decreases.